EVALUATING THE TYPE AND STATE OF ALASKA TAIGA FORESTS WITH IMAGING RADAR FOR USE IN ECOSYSTEM MODELS

Changes in the seasonal CO2 flux of the boreal forests may result from increased atmospheric CO2 concentrations and associated global warmin g patterns. To monitor this potential change, a combination of informa tion derived from remote sensing data, including forest type and growi ng season length, and ecophysiological models which predict the CO2 fl uX and its seasonal amplitude based on meteorological data, are requir ed. In this paper we address the use of synthetic aperture radar (SAR) to map forest type and monitor canopy and soil freeze/thaw, which def ine the growing season for conifers, and leaf on/off, which defines th e growing season for deciduous species. Aircraft SAR (AIRSAR) data col lected in March 1988 during a freeze/thaw event are used to generate s pecies maps and to determine the sensitivity of SAR to canopy freeze/t haw transitions. These data are also used to validate a microwave scat tering model which is then used to determine the sensitivity of SAR to leaf on/off transitions and soil freeze/thaw. Finally, a CO2, flux al gorithm is presented which utilizes SAR data and an ecophysiological m odel to estimate CO2 flux. CO2 flux MaPS are generated, from which are al estimates Of CO2 flux are derived.